Assembly For Coupling A Patient Reference Array To A Medical Implant Such As A Pedicle Screw

ABSTRACT

In an embodiment, a system attaches a patient reference array of a computer-assisted surgery system to a patient. The system includes a fixation post having a shaft having proximal and distal ends that are offset from. A threaded fastener is coupled to the shaft at the distal end that rotates relative to the shaft so as to engage internal threads of a pedicle screw, thereby causing the distal end of the shaft to translate in the anchor seat and urge the pedicle screw to transition from an unlocked configuration to a locked configuration. The attachment assembly has an arm that supports the patient reference array, and a coupler supported by the arm. The coupler has a fixation body that defines a recess that receives at least a portion of the fixation post, and an actuator that secures the attachment assembly to the fixation post.

BACKGROUND

Computer-assisted surgery employs computer technology for surgicalplanning and for guiding surgical instruments during a surgery.Typically, in performing a computer-assisted surgery, athree-dimensional model of the patient is generated using medicalimaging technologies such as one or more of Mill, CT scan, x-rays, andultrasound. Sensors are positioned over the patient, and a computersystem tracks movement of the surgical instruments relative to thethree-dimensional model of the patient as the surgical instruments aresensed by the sensors. To aid in tracking movement of the surgicalinstruments, a patient reference array is typically attached to thepatient prior to image collection that provides at least one referencepoint. Positioning of the instruments can then be tracked by thecomputer system relative to the at least one reference point. Surgeriesperformed using computer-assisted surgery techniques can typicallyreduce an amount of x-ray exposure to the patient compared toconventional non-computer assisted surgery techniques, and can oftenresult in more accurate placement of medical implants.

SUMMARY

In accordance with one aspect of the present disclosure, a system isconfigured to attach a patient reference array of a computer-assistedsurgery system to a patient. The system comprises a fixation post havinga shaft that has a proximal end and a distal end that are offset fromone another along a central axis. The fixation post has a threadedfastener at the distal end that is coupled to the shaft. The threadedfastener is configured rotate relative to the shaft about the centralaxis so as to engage threads of an anchor seat of a pedicle screw,thereby causing the distal end of the shaft to translate into the anchorseat along the central axis and urge the pedicle screw to transitionfrom an unlocked configuration to a locked configuration. In theunlocked configuration, a screw of the pedicle screw is configured topivot relative to the anchor seat of the pedicle screw. In the lockedconfiguration, a position of the screw is fixed relative to the anchorseat of the pedicle screw. The system further comprises an attachmentassembly that comprises an arm configured to support the patientreference array, and a coupler supported by the arm. The couplercomprises a fixation body defining a recess that is configured toreceive at least a portion of the fixation post, and an actuator that isconfigured to secure the attachment assembly to the fixation post.

In accordance with another aspect of the disclosure, an attachmentassembly is configured to attach a reference array of acomputer-assisted surgery system to a medical implant. The attachmentassembly comprises an arm configured to support the reference array, anda coupler. The coupler comprises a fixation body supported by the arm.The fixation body has a first end and a second end that are spaced fromone another along a central axis. The fixation body has an inner surfacethat defines a recess that extends into the first end and terminatesbefore the second end. The recess is configured to receive a proximalend of a shaft of the medical implant therein along the central axis.The attachment assembly further comprises an actuator coupled to thefixation body. The actuator has a shaft that extends into the recess andthat is configured to be received in bore hole that extends into theproximal end of the shaft of the medical implant so as to secure thefixation body to the shaft of the medical implant.

In accordance with yet another aspect of the present disclosure, anattachment assembly is configured to attach a reference array of acomputer-assisted surgery system to a medical implant. The attachmentassembly comprises an arm configured to support the reference array,where at least a portion of the arm extends along a central axis. Theattachment assembly comprises a coupler supported by the arm andconfigured to couple to the medical implant. The coupler comprises afixation body movably coupled to the arm such that the fixation body isconfigured to translate along at least a portion of the arm along thecentral axis. The fixation body defines a recess that is configured toreceive at least a portion of the medical implant. The coupler comprisesan actuator that is coupled to the fixation body such that actuation ofthe actuator causes the fixation body to translate along the arm alongthe central axis so as to secure the fixation body to the medicalimplant.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description of the illustrative embodiments may be betterunderstood when read in conjunction with the appended drawings. It isunderstood that potential embodiments of the disclosed systems andmethods are not limited to those depicted. In the figures:

FIG. 1 shows a perspective view of a system of attaching a patientreference array to a pedicle screw that is implanted in a patientaccording to one embodiment, the system including a fixation post and anattachment assembly that couples the patient reference array to thefixation post;

FIG. 2 shows a perspective view of a reference array body of the patientreference array of FIG. 1 according to one embodiment, the referencearray body supporting a plurality of spherical markers;

FIG. 3 shows an exploded perspective view of a bone anchor and collet ofthe pedicle screw of FIG. 1 according to one embodiment;

FIG. 4 shows a perspective view of an anchor seat of the pedicle screwof FIG. 1 according to one embodiment;

FIG. 5 shows an exploded perspective view of the fixation post of FIG. 1according to one embodiment;

FIG. 6 shows a perspective view of the fixation post of FIG. 1 engaginga collet of the pedicle screw of FIG. 1 according to one embodiment;

FIG. 7 shows a cross-sectional view of the fixation post and pediclescrew of FIG. 1 according to one embodiment, with the bone screw of thepedicle screw being in an unlocked position in which the bone screw ispermitted to pivot;

FIG. 8 shows a cross-sectional view of the fixation post and pediclescrew of FIG. 1 according to one embodiment, with the bone screw of thepedicle screw being in a locked position such that a position of thebone screw is fixed relative to an anchor seat of the pedicle screw;

FIG. 9 shows a perspective view of an adapter of the patient referencearray of FIG. 1 according to one embodiment, the adapter adapted tocouple the reference array body of the patient reference array to theattachment assembly;

FIG. 10 shows an exploded perspective view of the adapter of FIG. 9according to one embodiment;

FIG. 11 shows a perspective view of a system of attaching a patientreference array to a pedicle screw according to another embodiment, thesystem including a fixation post and an attachment assembly that couplesthe patient reference array to the fixation post;

FIG. 12 shows an exploded perspective view of the attachment assembly ofFIG. 11 according to one embodiment;

FIG. 13 shows a cross-sectional view of the attachment assembly of FIG.11 according to one embodiment;

FIG. 14 shows a perspective view of the attachment assembly of FIG. 1according to one embodiment;

FIG. 15 shows an exploded perspective view of the attachment assembly ofFIG. 1 according to one embodiment;

FIG. 16 shows a cross-sectional view of the attachment assembly of FIG.1 according to one embodiment;

FIG. 17 shows a perspective view of a system of attaching a patientreference array to a pedicle screw according to yet another embodiment,the system including a fixation post and an attachment assembly thatcouples the patient reference array to the fixation post;

FIG. 18 shows a perspective view of the attachment assembly of FIG. 17according to one embodiment;

FIG. 19 shows an exploded perspective view of the attachment assembly ofFIG. 17 according to one embodiment; and

FIG. 20 shows a cross-sectional view of the attachment assembly of FIG.17 according to one embodiment.

DETAILED DESCRIPTION

Typically, when performing a computer-assisted spinal surgery, thepatient reference array is either clamped onto a spinous process orattached to a dedicated pin or Schanz screw that is attached to thepelvic crest or a spinous process. The pin or Schanz screw is used onlyfor supporting the reference array, and therefore, implantation of thepin or Schanz screw can require an additional incision to be made thatmight not otherwise be needed in a conventional, non-computer-assistedsurgery. The additional incision can result in pain and irritation atthe additional incision site. Further, the use of a dedicated pin orSchanz screw can leave holes in a bone, which could weaken the bonethereby preventing future attachment of implants should they be needed.

Instead of attaching the patient reference array to a dedicated pin orSchanz screw, the patient array can be attached to a medical implant,such as a pedicle screw assembly, that was either previously implantedduring a prior spine fixation procedure or is being implanted for acurrent spine fixation procedure. Consequently, a separate incision neednot be made to affix the patient reference array. The pedicle screw canbe a monoaxial pedicle screw or a polyaxial pedicle screw. In the lattercase, a position of the pedicle screw should be fixed so that thepatient reference array does not move during the surgical procedure.Movement of the patient reference array can cause the computer-assistedsurgical system to lose accuracy and/or calibration, thereby resultingin a time delay to recalibrate the system or errors in placement ofmedical implants. Therefore, embodiments of the present disclosurerelate to systems that are configured to securely affix a patientreference array to a medical implant such as a pedicle screw so as toavoid movement of the patient reference array relative to the patientanatomy during a surgical procedure.

Referring to FIGS. 1, 11, and 17, according to various embodiments ofthe present disclosure, a system 10 is configured to attach a patientreference array 100 of a computer-assisted surgery system to a patient,such as a vertebra 12 of the patient. In general, the system 10comprises at least one, such as both, of (i) a fixation post 300 thatcouples to a bone fixation element 200, such as a pedicle screw, and(ii) an attachment assembly (e.g., 400, 600, 700) that couples a patientreference array 100 to at least one of the bone fixation element 200 andthe fixation post 300. The attachment assembly (e.g., 400, 600, 700) isconfigured to attach the patient reference array 100 to a medicalimplant, such as at least one of the bone fixation element 200 and thefixation post 300, so as to provide a rigid fixation between theattachment assembly and the medical implant. In some embodiments, thesystem 10 can further include at least one, such as both, of the patientreference array 100 and the bone fixation element 200.

Referring to FIG. 2, the patient reference array 100 can include areference array body 102 that supports a plurality of markers 104. Themarkers 104 can be positionally fixed relative to the reference arraybody 102 when the markers 104 are coupled to the reference array body102, such that movement of the reference body 102 causes correspondingmovement of the markers 104. The plurality of markers 104 define atleast one reference point that is detectable by a computer of thecomputer-assisted surgery system so that movement of a surgicalinstrument can be navigated relative to the at least one referencepoint. The plurality of markers 104 can include at least two markers104, such as at least three markers 104, or such as at least fourmarkers 104. Each marker 104 can be a protrusion that can have anysuitable shape. For example, each marker can have a spherical shape or apartially spherical shape. Each marker 104 can be a passive marker, suchas a reflective marker, that can be detected by at least one sensor orcamera of the computer-assisted surgery system without activelycommunicating with the computer of the computer-assisted surgery system.Alternatively, each marker can be an active marker that is configured toactively communicate with the computing device of the computer-assistedsurgery system.

The reference array body 102 can include a first end 106 and a secondend 108 that are offset from one another. The first end 106 can beconfigured to removably couple to the attachment assembly (e.g., 400,600, 700). For example, the first end 106 can define a shaft that isconfigured to couple to the attachment assembly. In some embodiments, atleast a portion of the first end 106 can have a non-circularcross-section that is configured to engage with a non-circularcross-section of an adapter 500 or the attachment assembly so as toprevent rotation of the reference array 100 relative to the attachmentassembly. For example, the non-circular shape can be a hexagon, anoctagon, or any other polygon or suitable shape. It will be understood,however, that the first end 106 can define other suitable shapes or canbe fixedly attached to the attachment assembly, such as monolithic with,adhered to, welded to, or otherwise fixedly attached to the attachmentassembly.

The reference array body 102 can support the plurality of markers 104such that the plurality of markers 104 are aligned in a common plane. Inone embodiment, as shown, the markers 104 can be supported so as todefine a triangle that connects the geometric centers of the markers104. For example, the reference array body 102 can have a Y-shape orT-shape. The Y- or T-shaped body 102 can have a first shaft 110 thatextends from the first end 106 towards the second end 108 along acentral axis D. The first shaft 110 can support a first marker 104(1) ofthe plurality of markers 104. The first marker 104(1) can be supportedadjacent the first end 106. The reference array body 102 can have asecond shaft 112 and a third shaft 114 that extend from opposed sides ofthe first shaft 110. The second and third shafts 112 and 114 can supportsecond and third markers 104(2) and 104(3) of the plurality of markers104, respectively. The second and third markers 104(2) and 104(3) can besupported at the second end 108. The first and second markers 104(1) and104(2) can be aligned along a first line L1. The second and thirdmarkers 104(2) and 104(3) can be aligned along a second line L2. Thefirst and third markers 104(1) and 104(3) can be aligned along a thirdline L3. At least one, up to all, of the first, second, and third linescan be angularly offset from one another. For example, the first andsecond lines L1 and L2 can define an angle therebetween that is lessthan or equal to 90 degrees. The second and third lines L2 and L3 candefine an angle therebetween that is less than or equal to 90 degrees.The first and third lines L1 and L3 can define an angle therebetweenthat is less than or equal to 90 degrees. It will be understood that, inalternative embodiments, the reference array body 102 can have othersuitable shapes and/or the markers 104 can be supported so as to defineother suitable shapes.

Turning now to FIGS. 3 and 4, an example bone fixation element 200 isshown. It will be understood that other bone fixation elements 200 arecontemplated within the scope of the present disclosure, and that thepresent disclosure is not limited to use with the bone fixation element200 shown in FIGS. 3 and 4. The bone fixation element 200 can comprise abone anchor seat 202, a collet 250 configured to be disposed inside theanchor seat 202, and a bone anchor 270. The bone anchor 270 can includea head 274, and a shank 272 that extends from the head 274 along acentral axis B. The head 274 can be enlarged to have a dimension along aradial direction that extends radially from the central axis B that isgreater than a dimension of the shank 272 along the radial direction.The head 274 can be configured to be received in the anchor seat 202. Insome examples, the head 274 can have a spherical shape, apartially-spherical shape such as a semi-spherical shape, or canalternatively have any suitable shape as desired to facilitate rotationwith respect to the collet 250 as is described in more detail below. Thehead 274 can include a drive surface 276 configured to receive acorresponding tip of a drive tool, such as a screw driver configured torotate the bone anchor 270 into engagement with the vertebrae 12 orother underlying bone surface. The drive surface 276 can define ahexagon, a star drive pattern, a Phillips head pattern, a slot for ascrew driver, threads configured to receive corresponding threads of athreaded drive post, or any suitable drive tool engaging structure asdesired.

The shank 272 can be attached at its upper end to the head 274. In atleast some embodiments, the bone anchor 270 can be configured as a bonescrew. Thus, the shank 272 can include external threading along at leasta portion, such as an entirety, of the shank 272. The shank can defineany suitable diameter, length, and thread design so as to engage theunderlying bone, such as a vertebra 12. Alternatively, the shank 272 canbe unthreaded so as to define a pin or a nail if desired. Thus, oneskilled in the art will appreciate that the bone anchor 270 is notlimited to any particular type of shank 272. The bone anchor 270 may becannulated such that a central bore extends through the bone anchor 270along the central axis B, or the bone anchor 270 may be solid along thecentral axis B (i.e., un-cannulated). In cannulated embodiments, thebone anchor 270 can optionally be fenestrated such that openings extendradially outward from the central bore to urge fluid out of the boneanchor 270 during injection or draw fluid into the central bore from theradial sides of the bone anchor 270 during extraction of materialadjacent the bone anchor 270 if desired.

Referring more specifically to FIG. 4, the anchor seat 202 includes ananchor seat body 204. The anchor seat body 204 can be a generallytubular body extending along a central axis A. The body 204 includes abase 206 and a pair of arms 208 that extend out (up in illustrated theorientation) from the base 206. The arms 208 are spaced opposite oneanother so as to define a rod-receiving channel 210 therebetween. Thearms 208 can be a mirror image of one another or can be a substantialmirror image of one another. As illustrated, each arm 208 can have anarc shape with an axis of the arc passing through a plane of symmetrythat bisects the anchor seat 202. Each arm 208 extends circumferentiallyabout its axis less than 180°, such as between 60° and 150°, forinstance approximately 90°.

Each arm 208 has a first or upper end 212 and a second or lower end 214that are offset from one another. The first or upper ends 212 define anupper end of the body 204. The upper end of the body defines an upperopening 216. The upper opening 216 can be defined between the first orupper ends 212 of the arms 208. The second or lower ends 214 of the arms208 are attached to the base 206. The base 206 defines a lower end 218that also defines the lower end of the body 204. The lower end 218defines a lower opening 220. The body 204 defines an axial bore 219extending from the lower opening 220 to the upper opening 216. The axialbore 219 is configured to receive the head 274 of the bone anchor 270such that the shank 272 of the bone anchor 270 extends out the loweropening 220.

The arms 208 each have opposed circumferentially outer ends. The body204 defines a pair of opposing gaps G that are spaced opposite from oneanother. Each gap is disposed between circumferentially adjacent outerends of the arms 208. The opposing gaps G are in alignment with theaxial bore 219. The arms 208 can be disposed radially opposite eachother such that the gaps G, in combination with the aligned portion ofthe axial bore 219, define the rod-receiving channel 210. Therod-receiving channel 210 is sized and configured to receive a spinefixation rod such that the spine fixation rod extends through the anchorseat 202. The spine fixation rod can thus extend through the opposinggaps G and the axial bore 219. The arms 208 define radially inner andouter surfaces. The inner surface of each arm 208 has internal threadingthereon. The threading is configured to threadedly receive a locking cap(not shown).

The base 206 includes a pair of spaced opposing support walls 222 and apair of spaced opposing spacer walls 224 connected between the supportwalls 222. The arms 208 extend up from respective support walls 222,such that the spacer walls 224 are disposed between the arms 208. Eachof the spacer walls 224 defines an upper end 226 that can be shaped asdesired. The upper end 226 of each spacer wall 224 can be curved inaccordance with the illustrated embodiment, such that the upper end 226and the circumferentially outer ends of the arms 208 are adjoined togenerally define a U-shape from a horizontal view through the gaps G.Thus, the upper ends 226 define the lower end of the gaps G. The upperends 226 can be shaped to conform generally with the outer surface ofthe spine fixation rod, such that the gaps G receive the spine fixationrod during use. In one embodiment, the upper ends 226 can be spacedslightly below the upper surface of the collet 250, such that the spinefixation rod engages the collet 250 during use. Thus, the spine rod canbias the collet 250 towards the lower end 218 of the anchor seat 202,thereby locking a position of the bone anchor 270 relative to the anchorseat 202.

In some embodiments, the bone anchor seat 202 can include a pair ofextension tabs 228 that are opposite one another. The extension tabs 228are spaced opposite one another so as to define an upper portion of therod-receiving channel 210 therebetween. Thus, the rod-receiving channel210 can have an upper portion defined between the extension tabs 228 anda lower portion defined between the arms 208, where the upper and lowerportions are aligned with one another along a direction that is parallelto the central axis A. The extension tabs 228 can be a mirror image ofone another or can be a substantial mirror image of one another. Asillustrated, each extension tabs 228 can have an arc shape with an axisof the arc passing through a plane of symmetry that bisects the anchorseat 202. Each extension tab 228 extends circumferentially about itsaxis less than 180°, such as between 60° and 150°, for instanceapproximately 90°. Thus, each extension tab 228 can have across-sectional shape that is substantially identical to, or similar to,a corresponding one of the arms 208.

Each extension tab 228 has a first or upper end 232 and a second orlower end 234 that are offset from one another. Each extension tab 228can be elongate from its upper end 232 to its lower end 234. The upperends 232 can define an upper end of the anchor seat 202. The lower end234 of each extension tab 228 can be attached to a respective one of thearms 208, such as to an upper end 212 of a respective one of the arms208. Each extension tab 228 can be removably attached to a respectivearm 208. For example, each extension tab 228 can be configured to breakaway from its respective arm 208. Thus, the anchor seat 202 can define ajoint between each extension tab 228 and its corresponding arm 208 thatis configured to facilitate separation of the extension tab 228 and arm208. In one example, each arm 208 can define a thickness from its innerwall to its outer wall, each extension tab 228 can define a thicknessfrom its inner wall to its outer wall, and each joint can define athickness from its inner wall to its outer wall that is less than thethicknesses of its corresponding arm 208 and extension tab 228. Theinner wall of each extension tab 228 can include internal threading atits lower end 234.

Referring back to FIG. 3, the collet 250 includes a collet body 252 thatdefines a first or upper end 254 and a lower end 256 opposite from oneanother. The upper end 254 is sized and configured to contact or supportat least a portion of a spine fixation rod (not shown) when the spinefixation rod is received within a rod-receiving channel of the anchorseat 202. The second or lower end 256 is sized and configured to contactor otherwise engage, directly or indirectly, a portion of the boneanchor head 274. The collet body 252 defines an axial bore 258 extendingfrom the upper end 254 to the lower end 256. Thus, the collet body 252can have an annular cross-sectional shape. The axial bore 258 is alignedwith an axial bore 219 of the anchor seat 202 when the collet 250 isdisposed in the anchor seat 202.

The upper end 254 of the collet 250 can define radially opposingupwardly facing seat portions 260 having a curvature or semi-sphericalshape corresponding to the outer surface of the spine fixation rod (notshown). Therefore, the seat portions 260 can be configured to receive orotherwise support at least a portion (e.g., a lower portion) of thespine fixation rod. However, it will be understood that the upper end254 can have other suitable shapes. The lower end 256 of the collet 250has an inner surface 262 that defines a shape that conforms to the shapeof the anchor head 274. For example, the inner surface 262 can have apartially-spherical shape. Thus, the inner surface 262 is configured toreceive or otherwise engage at least a portion of the head 274. Inalternative embodiments, the collet 250 can have an expandable lower endthat includes, for example, spring fingers, where the expandable lowerend is configured expand so as to pop onto the anchor head 274.

As will be described in further detail below with regards to FIGS. 7 and8, the bone fixation element 200 can be configured such that, when theanchor head 274 of the bone anchor 270 is disposed in the anchor seat202, the anchor head 274 can be moved between an unlocked position and alocked position. In the unlocked position, the bone anchor 270 can beconfigured to rotate relative to the collet 250 and/or anchor seat 202about the central axis B. Additionally, or alternatively, in theunlocked position, the bone anchor 270 can be configured to pivotrelative to the collet 250 and/or anchor seat 202 about at least oneaxis that is perpendicular to the central axis B. In at least someembodiments, the bone anchor 270 can be polyaxially pivotable relativeto the collet 250 and/or the anchor seat 202 such that the bone anchor270 pivots about a plurality of axes that are perpendicular to thecentral axis B. In the locked position, the collet 250 can engage theanchor head 274 so as to lock a position of the bone anchor 270 relativeto the anchor seat 202.

Turning to FIGS. 5 and 6, the fixation post 300 comprises a fixationshaft 302 having a proximal end 304 and a distal end 306 that are offsetfrom one another. The fixation shaft 302 can be elongate from theproximal end 304 to the distal end 306 along a central axis C. Thedistal end 306 of the fixation shaft 302 is configured to be received inthe anchor seat 202 of the bone fixation element 200. In particular, thedistal end 306 can have a distal end surface 312 that is configured tobe received in the rod-receiving channel 210 between the arms 208 of theanchor seat 202. The distal end 306 can also be configured to engage thecollet 250. For example, the distal end 306 can be configured to bereceived in the upwardly facing seat portions 260 of the collet 250.Thus, the distal end surface 312 can be configured the engage theupwardly facing seat portions 260.

At least a portion of the fixation shaft 302 is sized to be receivedbetween the extension tabs 228 when the fixation shaft 302 is receivedin the anchor seat 202. For example, the fixation shaft 302 can have atleast one outer surface 314, such as a pair of opposed outer surfaces314, that are configured to face and/or engage inner surfaces of theextension tabs 228. The fixation shaft 302 can have a cross-sectionalshape that is conforms to a cross-sectional shape of the anchor seat 202such that, when the fixation shaft 302 is disposed in the anchor seat202, the fixation shaft 302 does not rotate relative to the anchor seat202. The fixation shaft 302 can have a length along the central axis Cthat is sized such that the proximal end 304 extends beyond the arms 208of the bone fixation element 200 (and optionally beyond the extensiontabs 228 of the bone fixation element 200 in the event that the bonefixation element 200 is implemented with the tabs 228) when the distalend 306 of the fixation shaft 302 is seated in the anchor seat 202.

The proximal end 304 of the fixation shaft 302 can have any suitableconfiguration. For example, the fixation shaft 302 can define an opening308 that extends into the proximal end 304 towards the distal end 306.The opening 308 can be configured to engage a protrusion of theattachment assembly (e.g., 400, 600, 700). For example, the opening 308can define internal threads at the proximal end 304 that are configuredto engage external threads of the attachment assembly (e.g., 400, 600,700) as will be discussed below. Additionally, or alternatively, thefixation shaft 302 can have an outer surface 310 at the proximal end 304that has a non-circular cross-section. The non-circular cross-sectioncan be configured to engage a non-circular cross-section of theattachment assembly (e.g., 400, 600, 700) so as to prevent relativerotation between the fixation shaft 302 and the attachment assembly(e.g., 400, 600, 700).

The fixation post 300 has a threaded fastener 350 adjacent the distalend 306 that is rotatably coupled to the fixation shaft 302. Thethreaded fastener 350 can have a generally cylindrical outer surfacewith external threading disposed thereon. The threaded fastener 350 canbe configured to rotate relative to the fixation shaft 302 about thecentral axis C. In one embodiment, the fixation shaft 302 can include adrive surface 352 at its proximal end that is configured to receive acorresponding tip of a drive tool, such as a screw driver configured torotate the threaded fastener 350. The drive surface 352 can define ahexagon, a star drive pattern, a Phillips head pattern, a slot for ascrew driver, threads configured to receive corresponding threads of athreaded drive post, or any suitable drive tool engaging structure asdesired. The opening 308 can extend from the proximal end 304 of thefixation shaft 302 to the threaded fastener 350 so as to allow a drivetool to extend into the fixation shaft 302 to engage the drive surface352 of the threaded fastener.

The threaded fastener 350 can be coupled to the fixation shaft 302 byany suitable fastener. For example, the distal end 306 of the fixationshaft 302 can include an opening 316 that extends into an outer surfaceof the fixation shaft 302 along a transverse direction that istransverse to the central axis C. The threaded fastener 350 can bedisposed in the opening 316. The threaded fastener 350 can extend beyondthe outer surface of the fixation shaft 302 on both sides of the opening316 such that the threads of the fastener 350 can engage the threads ofthe anchor seat 202. To secure the threaded fastener 350 to the fixationshaft 302, the threaded fastener 350 can define an aperture 354 thatextends into a distal end of the threaded fastener 350 therein along thecentral axis C, and the fixation post 300 can include an axle 360 thatis configured to extend from fixation shaft 302 into the aperture 354 ofthe threaded fastener 350 such that the threaded fastener 350 rotatesabout the axle 360. In alternative embodiments (not shown), the threadedfastener can be disposed about an outer surface of the fixation shaft302, such that the fixation shaft 302 defines an axle about which thethreaded fastener rotates.

Turning to FIGS. 7 and 8, the threaded fastener 350 is spaced from thedistal end surface 312 of the fixation shaft 302 such that the threadedfastener 350 is configured to engage internal threading of the anchorseat 202, such as at least one of (i) the internal threads of the arms208 of the anchor seat 202 and (ii) the internal threads of theextension tabs 228 of the anchor seat 202. Thus, the threaded fastener350 is configured rotate relative to the fixation shaft 302 so as toengage the internal threads of the anchor seat 202, thereby causing thefixation shaft 302 to translate along the central axis C relative to theanchor seat 202. In particular, rotation of the threaded fastener 350 ina first rotational direction relative to both the fixation shaft 302 andanchor seat 202 can cause the distal end 306 of the fixation shaft 302to translate into the anchor seat 202 along the central axis C. As thedistal end 306 translates further into the anchor seat 202, the distalend 306 urges the bone fixation element 200 to transition from anunlocked configuration in FIG. 7 to a locked configuration in FIG. 8. Inthe unlocked configuration, the bone anchor 270 can be configured torotate relative to the collet 250 and/or anchor seat 202 about thecentral axis B. Additionally, or alternatively, in the unlockedposition, the bone anchor 270 can be configured to pivot relative to thecollet 250 and/or anchor seat 202 about at least one axis that isperpendicular to the central axis B. In at least some embodiments, thebone anchor 270 can be polyaxially pivotable relative to the collet 250and/or the anchor seat 202 such that the bone anchor 270 pivots about aplurality of axes that are perpendicular to the central axis B. In thelocked position, a position of the bone anchor 270 is fixed relative tothe anchor seat 202. In one example, in the locked position, the distalend 306 of the post 300 urges the collet 250 downward into the anchorseat 202. The collet 250 in turn urges the anchor head 274 downwardsagainst an inner surface 230 of the anchor seat 202, thereby fixing aposition of the anchor head 274 relative to the anchor seat 202.

Turning now to FIGS. 9 and 10, the attachment assembly (e.g., 400, 600,700) can be configured to support the patient reference array 100. Forexample, the attachment assembly (e.g., 400, 600, 700) can be fixedlyattached to the patient reference array 100, such as monolithic with,adhered to, welded to, or otherwise fixedly attached to the patientreference array 100. Alternatively, the attachment assembly (e.g., 400,600, 700) can be removably couplable to the patient reference array 100.For example, as illustrated in FIGS. 1, 9, and 10, the system 10 caninclude an adapter 500 that is configured to removably couple theattachment assembly (e.g., 400, 600, 700) to the reference array body102 of the patient reference array 100. The adapter 500 can beimplemented as a StarLink adapter manufactured by Brainlab AG, or as anyother suitable adapter that can couple the attachment assembly (e.g.,400, 600, 700) to reference array body 102.

The system 10 can include a joint that is configured to enable thereference array 100 to be selectively rotated about at least one axis soas to allow the patient reference array 100 to be repositioned relativeto at least one sensor or camera of the computer-assisted surgerysystem. The joint can be implemented by the adapter 500 or anothersuitable component of the system 10. The joint can be configured toenable the reference array 10 to be selectively rotated about thecentral axis D of the patient reference array 100. Additionally, oralternatively, the adapter 500 can be configured to enable the referencearray 10 to be selectively rotated about the central axis E that isperpendicular to the axis D of the reference array 100. The adapter 500can be configured to lock a position of the reference array 100 afterthe reference array 100 has been selectively rotated.

With specific reference to FIGS. 9 and 10, the adapter 500 can include aclamp 502. The clamp 500 can be configured to move between an unclampedposition and a clamped position when the first end 106 of the referencearray body 102 is received therein. In the unclamped position, the clamp500 can permit the reference array body 102 to (i) translate relative tothe clamp 500 along a first direction that is parallel to the axis D ofthe patient array 100, and/or (ii) rotate relative to the clamp 500about the axis D. In the clamped position, the clamp 500 positionallyfixes the reference array body 102 relative to the clamp 502 withrespect to at least one, such as both, of (i) translation along thefirst direction that is parallel to the axis D of the patient referencearray 100, and (ii) rotation about the axis D.

The clamp 502 can include a first plate 504 and a second plate 506. Thefirst and second plates 504 and 506 can be offset from one another alongthe first direction. The first and second plates 504 and 506 can haveinner surfaces 508 that face one another. In one embodiment, the innersurfaces 508 and can define at least one notch 510 that extends into atleast one of the inner surfaces 508 and is configured to receive thefirst end 106 of the reference array body 102. For example, the innersurfaces 508 can define opposing notches 510. The at least one notch canhave a non-circular cross-section that is configured to engage anon-circular cross-section of the first end 106 of the reference arraybody 102 so as to prevent the reference array body 102 from rotatingwhen the clamp 500 is in the clamped position. For example, the at leastone notch can define a cross-sectional shape that is a hexagon, anoctagon, or any other polygon or suitable shape.

The clamp 502 can include a hinge 512 that couples the first and secondplates 504 and 506 to one another such that they are rotatable relativeto one another. The hinge 512 can be define a pivot axis F that extendsalong the first direction that is parallel to the axis D. Thus, thefirst and second plates 504 and 506 can be configured to pivot about thepivot axis F towards one another to the clamped position and away fromone another to the unclamped position.

The adapter 500 can include an actuator 501 configured to selectivelycontrol rotation of the reference array body 102 relative to theattachment assembly (e.g., 400, 600, 700) about an axis E that extendsalong a direction that is perpendicular to the axis D of the patientreference array 100. The actuator 501 can be configured to transitionbetween an unlocked configuration and locked configuration. In theunlocked configuration, the reference array 100 is permitted to rotaterelative to the attachment assembly (e.g., 400, 600, 700) about the axisE. In the locked configuration, the reference array 100 is rotationallyfixed relative to the attachment assembly (e.g., 400, 600, 700) withrespect to rotation about the axis E.

To support the locked and unlocked configuration, the actuator 501, andhence the adapter 500, can include a fastener 520 that is configured toattach the clamp 502 to the attachment assembly (e.g., 400, 600, 700).The fastener 520 can include a shaft 522 having a first end 524 and asecond end 526. The first end 524 can be configured to attach to theattachment assembly (e.g., 400, 600, 700). For example, the first end524 can include threading that is configured to engage threading of theattachment assembly (e.g., 400, 600, 700). The second end 526 caninclude a drive surface 528 that is configured to be engaged by a useror instrument to turn the fastener 520. In one example, the drivesurface 528 can define a handle. The drive surface 528 can be enlargedto have a cross-sectional dimension that is greater than across-sectional dimension of the shaft 522.

The first and second plates 504 and 506 can each define an aperture 514therethrough that is configured to receive the shaft 522 of the fastener520. The apertures 514 can be aligned with one another so as to receivethe shaft 522 therethrough. The fastener 520 extends through the clamp502 such that the first end 524 extends out of the first plate 504 is adirection that extends from the second plate 506 to the first plate 504,and the second end 526 extends out of the second plate 506, opposite thefirst end 524, along a direction that extends from the first plate 504to the second plate 506.

The adapter 500 can include a biasing element 540, such as a spring,that is disposed between the second end 526 of the fastener 520 (e.g.,the handle), and the second plate 506. The biasing element 540 can beconfigured to bias the fastener 520 along a direction that extends fromthe first plate 504 towards the second plate 506. Thus, the biasingelement 540 can be configured to urge the attachment assembly (e.g.,400, 600, 700) against the outer surface of the first plate 504 when thefastener 520 is attached to the attachment assembly (e.g., 400, 600,700).

The force exerted by the biasing element 540 between the first plate 504and the attachment assembly (e.g., 400, 600, 700) can be sufficient tolimit or prevent rotation of the reference array body 102 relative tothe attachment assembly (e.g., 400, 600, 700), and hence relative to thebone fixation element 200. In some embodiments, the adapter 500 and theattachment assembly (e.g., 400, 600, 700) can include mating geometriesthat mate with one another when the biasing element 540 biases theattachment assembly (e.g., 400, 600, 700) against the adapter 500 so asto prevent rotation of the body 102 of the patient reference array 100relative to the attachment assembly (e.g., 400, 600, 700). For example,the first plate 504 can include a surface geometry 511 on an outersurface 509 of the first plate 504 that is configured to engage acorresponding surface geometry (see, for example, geometry 412 in FIGS.12, 14, and 18) of the attachment assembly (e.g., 400, 600, 700). Thesurface geometry 511 can include a plurality of protrusions, such asteeth, that are spaced apart from one another by recesses. Theprotrusions and recesses of the surface geometry 511 can be configuredto mate with corresponding protrusions and recesses of the attachmentassembly (e.g., 400, 600, 700) so as to fix a rotational position of thereference array 100. The protrusions and recesses can extend radiallyfrom the aperture 514 of the first plate 504. The protrusions andrecesses can be offset from one another circumferentially around theaperture 514. It will be understood that the mating geometries can beconfigured in another manner.

In operation, an external force can be applied to the fastener 520 alongan actuation direction that extends from the second plate 506 towardsthe first plate 504 so as to compress the biasing element 540. This inturn causes the first end 524 of the fastener 520, and hence theattachment assembly (e.g., 400, 600, 700) attached to the first end 524,to move along the actuation direction such that the surface geometry ofthe attachment assembly (e.g., 400, 600, 700) disengages from thesurface geometry 511 of the adapter 500. While the external force isapplied, the body 102 of the patient reference array 100 can be rotatedrelative to the attachment assembly (e.g., 400, 600, 700) to a desiredposition. The external force can then be released so that the biasingelement 540 urges the attachment assembly (e.g., 400, 600, 700) againstthe adapter 500 so as to interlock the mating geometries of theattachment assembly (e.g., 400, 600, 700) and the adapter 500, therebyfixing a position of the reference array body 102 relative to theattachment assembly (e.g., 400, 600, 700).

Turning now to the embodiment of FIGS. 11 to 13, a system 10 is shownhaving an attachment assembly 600 that couples a patient reference array100 to a medical implant 200. The reference array 100, the medicalimplant 200, the fixation post 300, and the adapter 500 can each beimplemented as described above. The attachment assembly 600 includes anarm 402 configured to support the patient reference array 100, and acoupler 628 supported by the arm 402. The arm 402 can have a first end404 and a second end 406 that are offset from one another. The arm 402can define a shaft 414 that extends between the first and second ends404 and 406. The first end 404 can have a coupler 408 that is configuredto couple to the patient reference array 100. In one example, thecoupler 408 can define an opening 410 that is configured to receive thefastener 520 of the adapter 500 (see FIGS. 9 and 10). For example, theopening 410 can include internal threading that engages the threading ofthe first end 524 of the fastener 520 of the adapter 500. However, itwill be understood that the first end 404 can be otherwise configured tocouple to the patient reference array 100. In alternative embodiments,the arm 402 can be fixedly attached to the reference array body 102,such as monolithic with, adhered to, welded to, or otherwise fixedlyattached to the reference array body 102.

The coupler 408 can include a surface geometry 412 on an outer surfaceof the arm 402 that is configured to engage a corresponding surfacegeometry 511 of the adapter 500. The surface geometry 412 can include aplurality of protrusions, such as teeth, that are spaced apart from oneanother by recesses. The protrusions and recesses can extend radiallyfrom the opening 410. The protrusions and recess can becircumferentially offset from one another about the opening 410.However, it will be understood that the surface geometry 511 can beconfigured in another manner. The protrusions and recesses of thesurface geometry 412 can be configured to mate with correspondingprotrusions and recesses of the adapter 500 so as to fix a rotationalposition of the reference array 100 relative to the attachment assembly600, and hence relative to the pedicle screw 200.

The coupler 628 can comprise a fixation body 630 and an actuator 650.The fixation body 630 can be attached to the arm 402 at the second end406. For example, the fixation body 630 can be fixedly attached to thearm 402 as shown or can be removably attached to the arm 402. Thefixation body 630 has a first end 632 and a second end 634 that arespaced from one another along a central axis H. The fixation body 630can have an outer surface 636 that extends between the first end 632 andthe second end 634. The outer surface 636 can be curved such that thefixation body 630 has a cylindrical shape, although it will beunderstood that the fixation body 630 can have any other suitable shapesuch as (without limitation) a cube. The arm 402 can extend from theouter surface 636. In some examples, the arm 402 can have an axis thatintersects the central axis of the H.

The fixation body 630 has an inner surface 638, opposite the outersurface 636. The inner surface 638 defines a fixation body recess 640that extends into the first end 632 towards the second end 634. Therecess 634 can terminate before the second end 634, such as at an innersurface of the second end 634. The recess 640 is configured to receivean end of a shaft of a medical implant, such as the proximal end 304 ofthe fixation shaft 302 of the fixation post 300, along a direction thatextends along the central axis H. In at least some embodiments, theinner surface 638 can have a non-circular cross-section. Thenon-circular cross-section can be configured to engage a non-circularcross-section of outer surface 310 of the proximal end 304 of the post300 so as to prevent relative rotation between the post 300 and theattachment assembly 600. In some examples, the fixation body 630 canextend along a perimeter of the recess 640 on four sides of the recess640. In some such examples, the fixation body 630 can be solid around anentire perimeter of the recess 640 (e.g., circumferentially solid) suchthat the fixation body 630 has a cross-section that defines a closedshaped. Thus, the fixation body 630 can be configured such that theshaft of the medical implant (e.g., the post 300) can only be receivedinto the recess 634 along a direction that extends along the centralaxis H.

The attachment assembly 600 can include an actuator 650 that isconfigured to secure the fixation body 630 to the medical implant. Theactuator 650 can include a shaft 652 having a first end 654 and a secondend 656. The second end 634 of the fixation body 630 can define anopening 642 that extends therethrough that is configured to receive theshaft 652. The first end 654 of the shaft 652 can be configured toattach to the post 300. For example, the first end 654 can be configuredto be received in the opening 308 in the proximal end 304 of the post300 so as to secure the attachment assembly 600 to the post 300. Thefirst end 654 can include threading that is configured to engage thethreading of the opening 308 of the post 300. The second end 656 caninclude a drive surface 658 that is configured to be engaged by a useror instrument to turn the actuator 650. In one example, the drivesurface 658 can define a handle. The drive surface 658 can be enlargedto have a cross-sectional dimension that is greater than across-sectional dimension of the shaft 652. The cross-sectionaldimension of the drive surface 658 can be greater than a cross-sectionaldimension of the opening 642 such that the drive surface 658 cannot passthrough the opening 642.

When the fixation post 300 is received in the fixation body recess 640and the actuator 650 is received in the opening 308 of the proximal end304 of the fixation post 300, the proximal end 304 of the fixation post300 can interfere with the fixation body 630 so as to limit movement ofthe fixation body 630 relative to the fixation post 300 along adirection that extends from the second end 634 of the fixation body 630to the first end 632. Further, the actuator 650, such as the enlargeddrive surface 658 of the actuator 650 can interfere with fixation body630 so as to limit movement of the fixation body 630 along a directionthat extends from the first end 632 of the fixation body 630 to thesecond end 634. In this way, the enlarged drive surface 658 and theproximal end 304 of the fixation post 300 can trap the second end 634 ofthe fixation body 630 therebetween so as to limit movement of thefixation body 630 relative to the post 300 along the axis H.

Turning now to the embodiment of FIGS. 1 and 14 to 16, a system 10 isshown having an attachment assembly 400 that couples a patient referencearray 100 to a medical implant 200. The reference array 100, the medicalimplant 200, the fixation post 300, and the adapter 500 can each beimplemented as described above. In general, the attachment assembly 400includes an arm 402 that is configured to support the patient referencearray 100. At least a portion of the arm 402 extends along a centralaxis K. The attachment assembly 400 includes a coupler 430 supported bythe arm 402. The coupler 430 has a fixation body 432 and an actuator450. The fixation body 432 is movably coupled to the arm 402 such thatthe fixation body 432 is configured to translate along at least aportion of the arm 402 along the central axis K. The fixation body 432defines a fixation body recess 434 that is configured to receive atleast a portion of the medical implant. The actuator 450 is coupled tothe fixation body 432 such that actuation of the actuator 450 causes thefixation body 432 to translate along the arm 402 along the central axisK so as to secure the coupler 430 to a medical implant. The medicalimplant can be at least one of (i) the bone fixation element 200 and(ii) the fixation post 300 that couples to the bone fixation element200. For example, the coupler 430 can be configured to couple theattachment assembly 400 to the extension tabs 228 of the bone fixationelement 200 by engaging the extension tabs 228. As another example, thecoupler 430 can be configured to couple the attachment assembly 400 tothe proximal end 304 of the fixation post 300. It will be understoodthat the attachment assembly 400 can alternatively couple to medicalimplants other than the bone fixation element 200 and the fixation post300.

The arm 402 can have a first end 404 and a second end 406 that areoffset from one another. The first end 404 can be configured asdescribed above in relation to FIGS. 11 to 13. For example, the firstend 404 can include a coupler 408. The coupler 408 can be spacedopposite from the coupler 430. The arm 402 can define a shaft 414 thatextends between the first end 404 and the second end 406. In someembodiments, the shaft 414 can include a first portion 414 a and aseparate second portion 414 b (as shown) that are attached to oneanother. The first portion 414 a can include the first end 404, and thesecond portion 414 b can include the second end 406. In otherembodiments, the shaft 414 can be a single piece that is monolithic fromthe first end 404 to the second end 406.

The second end 406 can include at least one engagement member 416 havingan engagement surface 418 that is configured to engage the medicalimplant so as to secure the attachment assembly 400 to the medicalimplant. The coupler 430 can include the at least one engagement member416. The at least one engagement member 416, and hence the engagementsurface 418, can be fixedly attached to the shaft 414 with respect tomovement along the central axis K. When the medical implant is receivedin the fixation body recess 434 of the fixation body 432, movement ofthe fixation body 432 along the shaft 414 along the central axis K cancause the at least one engagement surface 418 to apply a locking forceto the medical implant, thereby locking a position of the medical devicewithin the fixation body recess 434.

For example, the at least one engagement member 416 can be configured tomove between a biased position and a relaxed position. The at least oneengagement member 416 can be configured to apply the locking force tothe medical device when in the biased position and release the lockingforce when in the relaxed position. The at least one engagement member416 can be resiliently biased towards the relaxed position. Thus,movement of the fixation body 432 along the shaft 414 along a firstdirection can cause the fixation body 432 to apply a biasing force tothe at least one engagement member 416 so as to move the at least oneengagement member 416 inwardly into the fixation body recess 434 fromthe relaxed position to the biased position such that the at least oneengagement member 416 applies the locking force to the medical implant.Further, movement of the fixation body 432 along the shaft 414 along asecond direction, opposite the first direction, can cause the fixationbody 432 to remove the biasing force, thereby allowing the engagementmember 416 to automatically and resiliently flex outwardly to therelaxed position so as to release the locking force from the medicalimplant.

In one example, as shown, the at least one engagement member 416 caninclude first and second engagement members 416. The first and secondengagement members 416 can have first and second inner engagementsurfaces 418, respectively. Each engagement member 416 can have an outersurface 424, opposite its inner engagement surface 418. The first andsecond engagement members can define first and second prongs of a yoke420, respectively. Movement of the fixation body 432 along the armcauses the first and second engagement members 416 to flex towards oneanother so as to apply a locking force to the medical implant. Thus, theshaft 414 can define a Y-shape with the top of the Y-shape being definedby the first and second engagement members 416. The first and secondinner engagement surfaces 418 can be offset from one another so as todefine a recess 422 therebetween. At least a portion of the recess 422can be disposed with the fixation body recess 434.

The first and second engagement surfaces 418 can be offset from oneanother along a transverse direction (such as a radial direction) thatis transverse to the central axis K. At least one, such as both, of thefirst and second engagement surfaces 418 is movable relative to theother one of the first and second engagement surfaces 418 between therelaxed position and the biased position. At least a portion of thefirst engagement surface 418 is spaced closer to at least a portion ofthe second engagement surface 418 in the biased position than in therelaxed position. Thus, the first and second engagement surfaces 418 canbe moved towards one another such that they apply a locking force toopposed sides of the medical implant, thereby locking a position of themedical implant relative to the attachment assembly 400.

Each engagement member 416 can define a first end 416 a that is attachedto a shaft body 414 of the shaft 414, and a second end 416 b that isfree from attachment to the shaft body 414. The first end 416 a candefine a hinge about which the engagement member 416 is configured toresiliently flex. Each engagement member 416 can extend away from thecentral axis K respect to both the axial direction and the transversedirection. Thus, the second end 416 b of each engagement member 416 canbe outwardly offset from the first end 416 a of the engagement member416 with respect to both the axial and transverse directions. In oneexample, each engagement member 416 can be curved or angled inwardly asit extends from its second end 416 b towards its first end 416 a. Thus,at least a portion of each inner engagement surface 418 can be concave.At least a portion of each outer surface 424 can be convex. The firstand second engagement members 416 can extend away from one another withrespect to the transverse direction.

The fixation body 432 can include an upper end 436 and a lower end 438that are offset from one another. The fixation body 432 can include aproximal end 440 and a distal end 442 that are offset from one another.The fixation body recess 434 can extend from the upper end 436 to thelower end 438 such that the fixation body recess 434 is open at theupper and lower ends 436 and 438. The fixation body recess 434 canextend from the distal end 442 towards the proximal end 440. Thefixation body recess 434 can terminate before the proximal end 440 suchthat the fixation body recess 434 is open at the distal end 442 but notat the proximal end 440. The fixation body 432 can include first andsecond prongs 444 that are offset from one another along the transversedirection. The first and second prongs 444 can define the fixation bodyrecess 434 therebetween.

The fixation body 432 can define an aperture 446 that extends from theproximal end 440 to the fixation body recess 434. The shaft 414 can bereceived through the aperture 444 such that at least a portion of the atleast one engagement member 416 is received in the recess 434 and aportion of the shaft 414 extends out of the proximal end 440 of thefixation body 432. For example, the second portion 414 b of the shaft414 can be received through the aperture 444 and into an axial bore 413in the first portion 414 a of the shaft 414. The fixation body 432 canbe movable along the shaft 414 along a first direction such that thefixation body 432 applies a biasing force to each of the at least oneengagement member 416. For example, the fixation body 432 can be movablesuch that the first and second prongs 444 apply a biasing force to theouter surface 424 of at least one of the first and second engagementmembers 416 so as to move at least one of the first and secondengagement members 416 towards the other one of the first and secondengagement members 416.

The actuator 450 can be positionally fixed to the fixation body 432 withrespect to translation along the central axis K. In one example, theactuator 450 can be rotatable relative to the fixation body 432 aboutthe central axis K. For example, the actuator 450 can define a knob. Theactuator 450 can have an opening 452 therethrough that is configured toreceive at least a portion of the shaft 414 therethrough. The opening452 can be threaded. Thus, the actuator 450 can be threadedly coupled tothreading 415 on the arm 402 such that rotation of the actuator 450causes actuator 450 to translate along the arm 402 along the centralaxis K, thereby urging the fixation body 430 to translate along thecentral axis K. The actuator 450 can include a drive surface 454 that isconfigured to be engaged by a user or instrument to turn the actuator450. It will be understood that, in alternative embodiments, theactuator 450 can have other suitable configurations other than a knob.

Turning now to the embodiment of FIGS. 17 to 20, a system 10 has anattachment assembly 700 that couples a patient reference array 100 to amedical implant 200. The reference array 100, the medical implant 200,the fixation post 300, and the adapter 500 can each be implemented asdescribed above. In general, the attachment assembly 700 includes an arm402 that is configured to support the patient reference array 100. Atleast a portion of the arm 402 extends along a central axis K. Theattachment assembly 700 includes a coupler 730 supported by the arm 402.The coupler 730 has a fixation body 732 and an actuator 750. Thefixation body 732 is movably coupled to the arm 402 such that thefixation body 732 is configured to translate along at least a portion ofthe arm 402 along the central axis K. The fixation body 732 defines afixation body recess 734 that is configured to receive at least aportion of the medical implant. The actuator 750 is coupled to thefixation body 732 such that actuation of the actuator 750 causes thefixation body 732 to translate along the arm 402 along the central axisK so as to secure the coupler 730 to a medical implant. The medicalimplant can be at least one of (i) the bone fixation element 200 and(ii) the fixation post 300 that couples to the bone fixation element200. For example, the coupler 730 can be configured to couple theattachment assembly 700 to the extension tabs 228 of the bone fixationelement 200 by engaging the extension tabs 228. As another example, thecoupler 730 can be configured to couple the attachment assembly 700 tothe proximal end 304 of the fixation post 300. It will be understoodthat the attachment assembly 700 can alternatively couple to medicalimplants other than the bone fixation element 200 and the fixation post300.

The arm 402 can have a first end 404 and a second end 406 that areoffset from one another. The first end 404 can be configured asdescribed above in relation to FIGS. 11 to 13. For example, the firstend 404 can include a coupler 408. The coupler 408 can be spacedopposite from the coupler 730. The arm 402 can define a shaft 414 thatextends between the first end 404 and the second end 406. In someembodiments, the shaft 414 can include a first portion 414 a and aseparate second portion 414 b (as shown) that are attached to oneanother. The first portion 414 a can include the first end 404, and thesecond portion 414 b can include the second end 406. In otherembodiments, the shaft 414 can be a single piece that is monolithic fromthe first end 404 to the second end 406.

The second end 406 can include at least one engagement member 716 havingan engagement surface 718 that is configured to engage the medicalimplant so as to secure the attachment assembly 700 to the medicalimplant. The engagement surface 718 can be an inner engagement surfacethat faces into the fixation body recess 734. In some examples, theengagement surface 718 can define a recess 720 therein that isconfigured to cradle (or at least partially conform to) the medicalimplant. The coupler 730 can include the at least one engagement member716. When the medical implant is received in the fixation body recess734 of the fixation body 732, movement of the fixation body 732 alongthe shaft 414 along the central axis K can cause the at least oneengagement surface 718 to apply a locking force to the medical implant,thereby locking a position of the medical device within the fixationbody recess 734 as will be further described below.

The at least one engagement member 716 can be movably coupled to theshaft 414 such that the at least one engagement member 716 can translaterelative to the shaft 414 along the axis K. For example, the at leastone engagement member 416 can be configured to move between a biasedposition and a relaxed position. The at least one engagement member 416can be resiliently biased towards the relaxed position. The coupler 730can include a biasing element 715, such as a spring, that biases the atleast one engagement member 716 inwardly into the fixation body recess734. The at least one engagement member 716 can be configured to moveoutwardly (e.g., towards the first end 404) when a biasing force isapplied to the engagement surface 718. The at least one engagementmember 716 can be configured to resiliently move inwardly (i.e., towardsthe recess 734) when the biasing force is removed. In alternativeembodiments, the at least one engagement member 716, and hence theengagement surface 718, can be fixedly attached to the shaft 414 withrespect to movement along the central axis K.

The fixation body 732 can include an upper end 736 and a lower end 738that are offset from one another, such as spaced opposite one another.The fixation body 732 can include a proximal end 740 and a distal end742 that are offset from one another, such as spaced opposite oneanother. The fixation body 732 can include a first side 744 and a secondside 746 that are offset from one another, such as spaced opposite oneanother. The first and second sides 744 and 746 can extend between theupper and lower ends 736 and 738 and between the proximal and distalends 740 and 742. The fixation body recess 734 can extend from the upperend 736 to the lower end 738 such that the fixation body recess 734 isopen at the upper and lower ends 736 and 738. The fixation body recess734 can extend from the first side 744 towards the second side 746. Thefixation body recess 734 can terminate before the second side 746 suchthat the fixation body recess 734 is open at the first side 744 but notat the second side 746. The fixation body 732 can define a secondengagement surface 748 that faces into the fixation body recess 734,such as towards the engagement surface 718. The fixation body recess 734can be defined between the second engagement surface 748 and theengagement surface 718. As shown, the fixation body 732 can define aU-shape or C-shape about the fixation body recess 734.

The fixation body 732 can define an aperture 745 that extends from theproximal end 740 to the fixation body recess 734. The shaft 414 can bereceived through the aperture 745 such that at least a portion of the atleast one engagement member 716 is received in the recess 734 and aportion of the shaft 414 extends out of the proximal end 740 of thefixation body 732. For example, the second portion 414 b of the shaft414 can be received through the aperture 745 and into an axial bore 413in the first portion 414 a of the shaft 414.

The fixation body 732 can be movable along the shaft 414 along a firstdirection (e.g., towards the first end 404) so as to move the engagementsurface 748 of the fixation body 732 towards the engagement surface 718of the engagement member 716. Thus, a distance between the engagementsurface 718 and the engagement surface 748 can be decreased. In sodoing, the engagement surface 718 of the engagement member and theengagement surface 748 of the fixation body 732 can apply opposingforces to opposing sides of the medical implant so as to lock a positionof the medical implant relative to the fixation body 732. The fixationbody 732 can be movable along the shaft 414 along a second direction(e.g., away from the first end 404), opposite the first direction, so asto increase a distance between the engagement surface 718 of theengagement member and the engagement surface 748 of the fixation body732. In so doing, the opposing forces applied to the opposing sides ofthe medical implant can be released.

The actuation 750 can be positionally fixed to the fixation body 732with respect to translation along the central axis K. In one example,the actuator 750 can be rotatable relative to the fixation body 732about the central axis K. For example, the actuator 750 can define aknob. The actuator 750 can have an opening 752 therethrough that isconfigured to receive at least a portion of the shaft 414 therethrough.The opening 752 can be threaded. Thus, the actuator 750 can bethreadedly coupled to threading 415 on the arm 402 such that rotation ofthe actuator 750 causes actuator 750 to translate along the arm 402along the central axis K, thereby urging the fixation body 730 totranslate along the central axis K. The actuator 750 can include a drivesurface 754 that is configured to be engaged by a user or instrument toturn the actuator 750. It will be understood that, in alternativeembodiments, the actuator 750 can have other suitable configurationsother than a knob.

The actuator 750 can have an actuator body 756 and a connector 756 thatis attached to the actuator body 756. The actuator body can define thedrive surface 754. The connector 756 is configured to secure theactuator 750 to the fixation body 732 such that the actuator 750 isfixed to the fixation body 732 with respect to translation along thecentral axis K and rotatable relative to the fixation body 732. Theconnector 756 can have a generally cylindrical shape with acircumferential groove 758 extending around a circumference of theconnector 756. For example, the connector 756 can have a shape similarto a spool. The connector 756 can have a central axis that is alignedwith the central axis K. The opening 752 can extend through theconnector 756 such that the connector 756 is configured to receive atleast a portion of the shaft 414 therethrough.

To secure the actuator 750 to the fixation body 732, the fixation body732 can define at least one, such as two, securement apertures 735 thatextend into at least one of the upper and lower surfaces 736 and 738 andtowards the other one of the upper and lower surfaces 736 and 738.Further, the coupler 730 can include at least one, such as two, rods 737that are configured to be received into the securement apertures 735 andinto engagement with the circumferential groove 758 of the actuator 750.For example, a pair of the rods 737 can be engaged with thecircumferential groove 758 or opposed sides of the connector 756. Theconnector 756, and hence the actuator body 756, are permitted to rotateabout the axis K as the at least one rod 737 rides along thecircumferential groove 758.

Although there has been shown and described the certain embodiments ofthe present disclosure, it will be readily apparent to those skilled inthe art that modifications may be made thereto which do not exceed thescope of the appended claims. The embodiments described in connectionwith the illustrated embodiments have been presented by way ofillustration, and the present invention is therefore not intended to belimited to the disclosed embodiments. Furthermore, the structure andfeatures of each the embodiments described above can be applied to theother embodiments described herein. Accordingly, those skilled in theart will realize that the invention is intended to encompass allmodifications and alternative arrangements included within the spiritand scope of the invention, as set forth by the appended claims.

It should be noted that the illustrations and descriptions of theexamples and embodiments shown in the figures are for exemplary purposesonly, and should not be construed limiting the disclosure. One skilledin the art will appreciate that the present disclosure contemplatesvarious embodiments. Additionally, it should be understood that theconcepts described above with the above-described examples andembodiments may be employed alone or in combination with any of theother examples and embodiments described above. It should further beappreciated that the various alternative examples and embodimentsdescribed above with respect to one illustrated embodiment can apply toall examples and embodiments as described herein, unless otherwiseindicated.

Unless explicitly stated otherwise, each numerical value and rangeshould be interpreted as being approximate as if the word “about,”“approximately,” or “substantially” preceded the value or range. Theterms “about,” “approximately,” and “substantially” can be understood asdescribing a range that is within 15 percent of a specified value unlessotherwise stated.

Conditional language used herein, such as, among others, “can,” “could,”“might,” “may,” “e.g.,” and the like, unless specifically statedotherwise, or otherwise understood within the context as used, isgenerally intended to convey that certain embodiments include, whileother embodiments do not include, certain features, elements, and/orsteps. Thus, such conditional language is not generally intended toimply that features, elements, and/or steps are in any way required forone or more embodiments or that one or more embodiments necessarilyinclude logic for deciding, with or without author input or prompting,whether these features, elements and/or steps are included or are to beperformed in any particular embodiment. The terms “comprising,”“including,” “having,” and the like are synonymous and are usedinclusively, in an open-ended fashion, and do not exclude additionalelements, features, acts, operations, and so forth. Also, the term “or”is used in its inclusive sense (and not in its exclusive sense) so thatwhen used, for example, to connect a list of elements, the term “or”means one, some, or all of the elements in the list.

While certain example embodiments have been described, these embodimentshave been presented by way of example only and are not intended to limitthe scope of the inventions disclosed herein. Thus, nothing in theforegoing description is intended to imply that any particular feature,characteristic, step, module, or block is necessary or indispensable.Indeed, the novel methods and systems described herein may be embodiedin a variety of other forms; furthermore, various omissions,substitutions, and changes in the form of the methods and systemsdescribed herein may be made without departing from the spirit of theinventions disclosed herein. The accompanying claims and theirequivalents are intended to cover such forms or modifications as wouldfall within the scope and spirit of certain of the inventions disclosedherein.

It should be understood that the steps of the exemplary methods setforth herein are not necessarily required to be performed in the orderdescribed, and the order of the steps of such methods should beunderstood to be merely exemplary. Likewise, additional steps may beincluded in such methods, and certain steps may be omitted or combined,in methods consistent with various embodiments of the present invention.

Although the elements in the following method claims, if any, arerecited in a particular sequence with corresponding labeling, unless theclaim recitations otherwise imply a particular sequence for implementingsome or all of those elements, those elements are not necessarilyintended to be limited to being implemented in that particular sequence.

What is claimed is:
 1. A system configured to attach a patient referencearray of a computer-assisted surgery system to a patient, the systemcomprising: a fixation post having a shaft that has a proximal end and adistal end that are offset from one another along a central axis, thefixation post having a threaded fastener adjacent the distal end that iscoupled to the shaft, the threaded fastener configured rotate relativeto the shaft about the central axis so as to engage threads of an anchorseat of a pedicle screw, thereby causing the distal end of the shaft totranslate into the anchor seat along the central axis and urge thepedicle screw to transition from an unlocked configuration, wherein ascrew of the pedicle screw is configured to pivot relative to the anchorseat of the pedicle screw, to a locked configuration, wherein a positionof the screw is fixed relative to the anchor seat of the pedicle screw;and an attachment assembly comprising: an arm configured to support thepatient reference array; and a coupler supported by the arm, the couplercomprising: a fixation body defining a recess that is configured toreceive at least a portion of the fixation post; and an actuator that isconfigured to secure the attachment assembly to the fixation post whenthe at least a portion of the fixation post is received in the recess.2. The system of claim 1, wherein the shaft is sized such that, when thedistal end of the shaft is received in the anchor seat, the shaft isreceived between extension tabs of the anchor seat and the proximal endof the shaft extends beyond the extension tabs.
 3. The system of claim1, wherein the distal end of the shaft includes an opening that extendsthrough an outer surface of the shaft along a transverse direction thatis transverse to the central axis, and the threaded fastener is disposedin the opening.
 4. The system of claim 1, wherein the shaft has an outersurface at the proximal end that has a non-circular cross-sectionconfigured to engage a non-circular cross-section of the attachmentassembly so as to prevent relative rotation between the shaft and theattachment assembly.
 5. The system of claim 1, wherein: the proximal endof the shaft defines a bore hole that extend towards the distal end ofthe shaft; and the fixation body has a first end and a second end thatare spaced from one another along a central axis, and the recess of thefixation body extends into the first end and terminates before thesecond end such that the recess is configured to receive the proximalend of the shaft along the central axis of the fixation body; and theactuator has a shaft that extends into the recess and that is configuredto be received in the bore hole of the fixation shaft so as to securethe fixation body to the fixation shaft.
 6. The system of claim 1,wherein: at least a portion of the arm extends along a central axis; thefixation body is movably coupled to the arm such that the fixation bodyis configured to translate along at least a portion of the arm along thecentral axis of the arm; and the actuator that is coupled to thefixation body such that actuation of the actuator causes the fixationbody to translate along the arm along the central axis of the arm so asto secure the fixation body to the fixation post.
 7. The system of claim6, wherein the system comprises first and second engagement members thatdefine first and second prongs of a yoke, respectively, and movement ofthe fixation body along the arm causes the first and second engagementmembers to flex towards one another so as to apply a locking force tothe medical implant when at least a portion of the medical implant isreceived between the first and second engagement members.
 8. The systemof claim 6, wherein: the arm includes a first engagement surface and thefixation body includes a second engagement surface, the first and secondengagement surfaces facing one another so as to define the recesstherebetween; and movement of the fixation body along a first directioncauses the second engagement surface to move towards the engagementsurface such that, when at least a portion of the medical implant isdisposed between the engagement surface and the second engagementsurface, the engagement surface and the second engagement surface applyopposing forces to opposing sides of the medical implant so as to lock aposition of the medical implant relative to the fixation body.
 9. Anattachment assembly configured to attach a reference array of acomputer-assisted surgery system to a medical implant, the attachmentassembly comprising: an arm configured to support the reference array;and a coupler comprising: a fixation body supported by the arm, thefixation body having a first end and a second end that are spaced fromone another along a central axis, the fixation body having an innersurface that defines a recess that extends into the first end andterminates before the second end, the recess configured to receive aproximal end of a shaft of the medical implant therein along the centralaxis; and an actuator coupled to the fixation body, the actuator havinga shaft that extends into the recess and that is configured to bereceived in bore hole that extends into the proximal end of the shaft ofthe medical implant so as to secure the fixation body to the shaft ofthe medical implant.
 10. The attachment assembly of claim 9, wherein thefixation body has an outer surface that extends between the first endand the second end, and the arm extends from the outer surface.
 11. Theattachment assembly of claim 10, wherein the arm extends at leastpartially along an axis that intersects the central axis of the fixationbody.
 12. The attachment assembly of claim 10, wherein the inner surfacehas a non-circular cross-section that is configured to engage anon-circular cross-section of an outer surface of the proximal end ofthe medical implant so as to prevent relative rotation between the shaftof the medical implant and the attachment assembly.
 13. The attachmentassembly of claim 9, wherein the fixation body is configured such thatthe shaft of the medical implant can only be received into the recessalong a direction that extends along the central axis.
 14. Theattachment assembly of claim 9, wherein the arm has a first end and asecond end that are offset from one another, the first end having acoupler that is configured to couple to the patient reference array, andthe second end being attached to the fixation body.
 15. An attachmentassembly configured to attach a reference array of a computer-assistedsurgery system to a medical implant, the attachment assembly comprising:an arm configured to support the reference array, at least a portion ofthe arm extending along a central axis; and a coupler supported by thearm and configured to couple to the medical implant, the couplercomprising: a fixation body movably coupled to the arm such that thefixation body is configured to translate along at least a portion of thearm along the central axis, the fixation body defining a recess that isconfigured to receive at least a portion of the medical implant; and anactuator that is coupled to the fixation body such that actuation of theactuator causes the fixation body to translate along the arm along thecentral axis so as to secure the fixation body to the medical implant.16. The attachment assembly of claim 15, wherein the arm has a first endand a second end that are offset from one another, and the second endincludes at least one engagement member having an engagement surfacethat is configured to apply a locking force to the medical implant so asto secure the attachment assembly to the medical implant.
 17. Theattachment assembly of claim 16, wherein, when the medical implant isreceived in the recess of the fixation body, movement of the fixationbody along the arm along the central axis causes the at least oneengagement surface to move inwardly with respect to the recess to applya locking force to the medical implant, thereby locking a position ofthe medical device within the recess.
 18. The attachment assembly ofclaim 16, wherein the at least one engagement member comprises first andsecond engagement members that define a yoke, and movement of thefixation body along the arm causes the first and second engagementmembers to flex towards one another so as to apply a locking force tothe medical implant when at least a portion of the medical implant isreceived between the first and second engagement members.
 19. Theattachment assembly of claim 16, wherein fixation body includes a secondengagement surface that faces the engagement surface so as to define therecess therebetween, and movement of the fixation body along a firstdirection causes the second engagement surface to move towards theengagement surface such that, when at least a portion of the medicalimplant is disposed between the engagement surface and the secondengagement surface, the engagement surface and the second engagementsurface apply opposing forces to opposing sides of the medical implantso as to lock a position of the medical implant relative to the fixationbody.
 20. The attachment assembly of claim 15, wherein the arm has afirst end and a second end that are offset from one another, the firstend having a coupler that is configured to couple to the patientreference array, and the second end being attached to the fixation body.